1. Field of the Invention
The present invention relates to a display apparatus for displaying a tone curve representing the characteristics of output image gradation values with respect to input image gradation values, and a tone curve adjusting apparatus for adjusting the tone curve displayed on the display apparatus in response to displayed image manipulations entered via a manual command input device.
2. Description of the Related Art
It has heretofore been customary in the art of printing and platemaking to generate a color proof carrying a color image on a proof sheet for examining colors and making color corrections, with a proofer such as a color printer or the like before a colored printed material with a color image printed on a print sheet is produced as a final finished product by a color printing machine such as a rotary press.
The proofer is used because it does not require films and printing plates that would be needed by printing machines and can easily generate as many hard copies carrying color images on proof sheets, i.e., color proofs, as required at a low cost within a short period of time.
In the production of color proofs, tone curves are adjusted to equalize the colors and densities of an image on a colored printed material and the colors and densities of an image on a color proof to each other with respect to image data that have been inputted to the proofer.
FIG. 8 of the accompanying drawings illustrates, by way of example, a displayed image for a conventional tone curve adjustment process on a display unit of a tone curve adjusting apparatus.
As shown in FIG. 8, the displayed image, denoted at 2, for tone curve adjustment has a grid of vertical and horizontal gradations spaced at intervals of 10%. The displayed image 2 also includes numerical values of xe2x88x9220, 0, +20 representing some of the horizontal gradations which indicate a full scale of dot gains over a range of xc2x120% along the vertical axis, and numeral values of 0, 10, 20, 50, 70, 90, 100 representing some of the vertical gradations which indicate a full scale of input image data gradations (input gradations) over a range from 0 to 100%.
The displayed image 2 further includes a tone curve 4 plotted against the gird of vertical and horizontal gradations. The shape of the tone curve 4 can be changed or adjusted by dragging any desired position on the tone curve 4 with a mouse used as an input device.
Usually, a range for correcting dot gains is about xc2x110%. Since the full scale of dot gains along the vertical axis extends over the range of xc2x120% in FIG. 8, desired dot gains can be adjusted and visually confirmed in the entire range from 0 to 100% of the full scale of input gradations along the horizontal axis.
There are instances where the user is desirous of confirming part of the tone curve, e.g., a highlight area in an image of skin color for which the human visual sensitivity is high, a shadow area in a scenery image at night, or an intermediate gradation area in a scenery image of leaves in early spring. In those situations, since the range (full scale) of input image gradation values of the conventional tone curve shown in FIG. 8 is wide, the user tends to find the tone curve difficult to visually grasp easily and quickly in confirming a partial range of the input image gradation values such as for a highlight area, a shadow area, or an intermediate gradation area, and also tends to find the tone curve hard to adjust or correct in a partial range of the input image gradation values.
It is therefore an object of the present invention to provide a display apparatus for displaying a tone curve such that even a partial range of the tone curve can be displayed for being visually grasped easily and quickly.
Another object of the present invention is to provide a tone curve adjusting apparatus for allowing even a partial range of input image gradation values to be adjusted and corrected finely.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example.